This represents a request for funds to continue PO1-GM31689. The central goals of this proposal concern the regulation of genes within multigene families, which represents the common interest among the four participating independent investigators. The powerful techniques of recombinant DNA technology are utilized by the four laboratories to study distinct groups of biologically important macromolecules. Most of these molecules are members of multigene families that are expressed in a developmentally-timed fashion. A key aspect of all projects is the tissue- specific regulation of protein production. The program project mechanism is requested as the technologies needed to carry out each individual project require not only the intellectual interaction of several investigators, but in addition, the pooling of resources and equipment. As this program project is submitted for its eleventh to fifteenth year of support, a very significant outcome of this funding mechanism has emerged. The four of us will be moving in approximately 10 months to occupy a floor of a biomedical research facility that is currently under construction. Despite our initial association with different departments and different graduate programs, we will be housed together as a "Molecular Immunology Center". This will further interactions both intellectual and physical and provides persuasive evidence of our long standing productive interaction.